Generally, a semiconductor die may be connected to other devices external to the semiconductor die through a type of packaging utilizing solder bumps. The solder bumps may be formed by initially forming a layer of underbump metallization on the semiconductor die and then placing solder onto the underbump metallization. After the solder has been placed, a reflow operation may be performed in order to shape the solder into the desired bump shape. The solder bump may then be placed into physical contact with the external device and another reflow operation may be performed in order to bond the solder bump with the external device. In such a fashion, a physical and electrical connection may be made between the semiconductor die and an external device, such as a printed circuit board, another semiconductor die, or the like.
However, the material that comprises the underbump metallization is merely one more type of material placed onto a stack of many different materials, such as dielectric materials, metallization materials, etch stop materials, barrier layer materials, and other materials utilized in the formation of the semiconductor die. Each one of these different materials may have a unique coefficient of thermal expansion that is different from the other materials. This type of coefficient of thermal expansion mismatch causes each one of the materials to expand a different distance when the semiconductor die is heated during later processing or use. As such, at elevated temperatures there is a coefficient of thermal expansion mismatch that causes stresses to form between the different materials and, hence, the different parts of the semiconductor die. This mismatch is especially prevalent between the underbump metallization and underlying metallization layers. If not controlled, these stresses can cause delamination to occur between the various layers of material, especially when the materials used include copper and a low-k dielectric layer. This delamination can damage or even destroy the semiconductor die during the manufacturing process or else during its intended use.
Corresponding numerals and symbols in the different figures generally refer to corresponding parts unless otherwise indicated. The figures are drawn to clearly illustrate the relevant aspects of the embodiments and are not necessarily drawn to scale.